.Your network contains an Active Directory domain named contoso.com.
Contoso.com contains a server named Server1 that has the Remote Desktop Session Host (RD Session Host) role service installed.
You install the Remote Desktop Licensing (RD Licensing) role service on a server named Server2.
Server2 is in a workgroup.
On Server1, you attempt to configure Server2 as the RD Licensing server and receive the error shown in the following message box.

You need to ensure that you can configure Server1 to use Server2 as the RD Licensing server.

What should you do first?

A.
Join Server1 to the workgroup.

B.
Join Server2 to the contoso.com domain.

C.
On Server2, activate the server from Remote Desktop Licensing Manager.

D.
On Server2, modify the membership of the Terminal Server Computers group.

Explanation:
Activating a Terminal Services License Server

A Terminal Services license server must be activated in order to certify the server and allow the license server to issue Terminal Services client access licenses (TS CALs). You can activate a license server by using the Activate Server Wizard in the TS Licensing Manager tool.

There are three methods by which you can activate your license server:

Internet (Automatic) This method requires Internet connectivity from the computer running TS Licensing Manager. Internet connectivity is not required from the license server itself. This method uses TCP/IP (TCP Port 443) to connect directly to the Microsoft Clearinghouse.
Web You can use the Web method when the computer running TS Licensing Manager does not have Internet connectivity, but you have access to the Web by means of a Web browser from another computer. The URL for the Web method is displayed in the Activate Server Wizard.
Telephone The telephone method allows you to talk to a Microsoft customer service representative to complete the activation process. The appropriate telephone number is determined by the country/region that you choose in the Activate Server Wizard and is displayed by the wizard.

When you activate the license server, Microsoft provides the server with a limited-use digital certificate that validates server ownership and identity. Microsoft uses an X.509 industry standard certificate for this purpose. By using this certificate, a license server can make subsequent transactions with Microsoft.

If a license server is not activated, the license server can only issue temporary TS Per Device CALs, which are valid for 90 days, or TS Per User CALs.

Source: http://technet.microsoft.com/en-us/library/cc731293.aspx